WDM optical network with passive pass-through at each node

Abstract

A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Description

[0001]This application is a continuation application of U.S. patent application Ser. No. 09 / 730,549, filed Dec. 7, 2000, now U.S. Pat. No. 6,563,615, which is a divisional application of U.S. patent application Ser. No. 09 / 372,576, filed Aug. 12, 1999, now U.S. Pat. No. 6,556,321, which is a divisional application of Ser. No. 08 / 917,784, filed Aug. 27, 1997, now U.S. Pat. No. 6,631,018.FIELD OF THE INVENTION[0002]The present invention relates to a method and apparatus for establishing communication over an optical network employing wavelength division multiplexing.BACKGROUND OF THE INVENTION[0003]The ever-increasing demand for bandwidth has spurred the growth of high speed transport networks. Currently, the key standard for use in such networks is SONET, which is an acronym for Synchronous Optical Network. The SONET standard defines a hierarchy of optical transmission rates over point-to-point and ring network topologies. For example, the SONET optical carrier—level 3 (OC-3) transmi...

AI Technical Summary

Benefits of technology

The present invention provides a communication network using wavelength division multiplexing (WDM) with optical transmission media capable of carrying a plurality of wavelengths organized into bands. The network is protocol and bit rate independent, more responsive to the demands of telecommunications carriers. The interface between nodes is a filter that separates out the band associated with the node and passes other bands. The network has low overall loss and requires no optical amplifiers. The optical path is passive except for nodes where wavelengths are added or dropped. The invention also provides a method of establishing communication over the network and an interface device for use in the network. The fiber optic WDM ring comprises a plurality of switching nodes and means for generating a plurality of wavelengths organized in to bands on the ring. The maintenance channel can be injected by modulating the bias current of the device generating the wavelengths.

Problems solved by technology

Unfortunately, this requirement of SONET to terminate the entire optical signal at every node makes upgrading the capacity of the ring a slow and costly process, because every node must be upgraded even though it may be that only one node requires the additional capacity.

Although this provides a SONET network with the ability to carry a variety of payloads, a new payload cannot be transported until a mapping is defined and the interface circuit is developed and deployed.

In addition, if there is insufficient spare capacity in the network to handle the new payload bit rate, then the entire network may have to be upgraded.

Thus, SONET networks are not responsive to the needs of today's services, which are demanding greater capacity and introducing a wide range of protocols.

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